The present invention is best put into perspective by the teachings of Anguillo et al, U.S. Pat. No. 3,816,616 (1974) which states in column 1 thereof, lines 20-52:
"The possibility of combining both shampoo and cream rinse action in a single composition for use in a single treatment of hair has been investigated by until now has been considered impractical. It is well known that anionic detergents and polymers are suitable for shampooing and that cationic detergents and polymers act as cream rinses in many instances. The difficulty which investigators have encountered where these two types of materials are contacted with one another is that they either precipitate or react with one another to the extent that their individual effectiveness is significantly impaired. This is so even if they remain in solution or in a suspended state. The incompatibility of anionic and cationic compounds is well recognized by workers in the art as indicated by Sagarin in Cosmetics, Interscience Publishers, New York, 1957, where it is stated on page 538 that anionic and cationic materials are not used in combination because they react to form salts. Thus, in practice, the anionic detergent shampoo is used first, followed by a separate cream rinse with a cationic material."
As a consequence, shampoos have since been prepared from foamy amphoteric compounds (having the capacity of behaving either as an acid or a base) and cationic compounds and cationic surface active agents. A separate cream rinse is applied, if desired, following rinsing of the shampoo composition from the hair, the cream rinse being used to condition the hair. This, of course, is time consuming and is not convenient. The results obtained in this matter also have not been fully satisfactory due to the difficulties associated with the deposition and retention on the hair of the hair conditioning aid. The inclusion of suitable hair conditioning agents in a shampoo therefore has certain attractive features.
For example, in U.S. Pat. No. 4,247,538 (1981) to Barker there is described an aqueous composition useful in shampooing and conditioning hair and containing an amphoteric shampoo base, a cationic surfactant and an anionic macrocolloid polymer (gum arabic). Upon rinsing, this composition deposited the macrocolloid polymeric component, providing desirable properties to the hair, such as body and curl retention.
Although such shampoos have been disclosed which contain conditioning aids, they have not been totally satisfactory for a variety of reasons. As noted, compatibility problems exist between good cleaning anionic surfactants and the fatty cationic agents which are good conditioning agents. This caused other surfactants, along with the amphoterics, to be considered by workers in the field, such as nonionics and zwitterionics. Others have attempted to carefully control pH in combination with polyethylene ester components, or neutralized fatty acids, which provided milder shampoo formulations. Such efforts are reflected in patents issued in the conditioning shampoo area. See, for example, U.S. Pat. No. 3,590,122 (1971) to Roberts et al; U.S. Pat. No. 3,808,329 to Bolich et al (1974); U.S. Pat. No. 3,849,348 (1974) to Hewitt; U.S. Pat. No. 3,990,991 (1976) to Gerstein; and U.S. Pat. No. 3,822,312 to Sato (1974).
More recently, U.S. Pat. No. 4,701,322 (1987) to Dixon et al described a conditioning shampoo where the conditioning agent is a saturated, straight chain fatty acid from about 14 to about 18 carbon atoms. U.S. Pat. No. 4,741,855 (1988) to Grote et al described conditioning shampoos which comprise a synthetic surfactant, an insoluble, non-volatile silicone, a suspending agent and water. This approach focused on maintaining a dispersed, insoluble silicon material in the aqueous shampoo medium by employing certain long chain acyl derivatives.
There have also been references to clear conditioning shampoos in various vendor brochures. For example, the water-white conditioning shampoo reported by Calgon is prepared via a batch mixing process combining 10.36% by weight of the active component of an anionic cleansing agent (sodium laureth-1-sulfate) with up to 0.8% by weight of the active component of the cationic conditioning agent Merquat 280 (a copolymer of dimethyldiallyl ammonium chloride and acrylic acid) and further incorporating cocomidopropyl betaine, sodium lauroyl sarcosinate, sodium chloride, fragrance and preservative. Citric acid is added to adjust the pH to 6.0. See Household and Personal Products Industries, 26(11), 16, (November 1989). The clear conditioning shampoo reported by Henkel is also prepared by a batch mixing process which combines 12.6% by weight of active ammonium lauryl sulfate with up to 0.9% by weight of a cationic conditioning agent hydroxycetyl hydroxyethyl dimonium chloride, further incorporating hydrolyzed animal protein as an additional conditioning component, cocamidopropyl amine oxide, fragrance, and preservative. The pH is adjusted to a range of 6.0 to 6.5 with citric acid. See the Product Information Bulletin, Henkel, Cospha Division, Clear Shampoo Conditioner Formula HOB-296-42-2.
While the above references disclose using anionic surfactants in combination with a cationic conditioning agent, they are not suggestive of compositions wherein through a particular combination of ingredients a clear product is produced which provides the functional properties of cleansing and conditioning the hair. Furthermore, the aforementioned references do not appreciate the limits of cationic conditioning agent that can be combined with an anionic cleansing agent to provide for an optically clear conditioning shampoo. In other words, the references fail to solubilize the now disclosed amounts of cationic conditioning agent per gram of anionic shampoo base detergent.
It is therefore an object of the present invention to provide a superior optically clear conditioning shampoo by incorporating the highest levels of cationic conditioning components in combination with anionic cleansing agents and avoiding problems of incompatibility and precipitation of the cationic and anionic compounds.
It is a further object of the present invention to provide a superior method wherein through a particular combination of anionic cleansing agents and cationic conditioning compounds problems of incompatibility and precipitation are avoided and an optically clear composition is produced.
A still further object of the present invention is to provide a superior method for cleaning and conditioning the hair.
Finally, the advantages of the present inventive combination include the convenience of treating the hair to a cleaning and conditioning action in a single step. Furthermore, the clarity of the system operates to clean and condition the hair without the use of insoluble fats, oils and waxes. The elimination of such insoluble components in the shampoo/conditioning matrix serves to provide a desired level of softness, good luster and manageability. These and other objects will become readily apparent from the detailed description which follows.
Unless otherwise indicated, all percentages and ratios herein are by weight.